Effectiveness of Various Sources of Nonessential Nitrogen in Promoting Growth of Chicks Fed Carbohydrate-containing and “Carbohydrate-free” Diets

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Abstract
Studies were conducted to compare the requirement of the chick for glutamic acid when fed “carbohydrate-free” and carbohydrate-containing diets, and to determine the effectiveness of other sources of nonessential nitrogen in meeting this requirement. Results showed that either L-glutamic acid or L-aspartic acid could serve as the major source of nonessential nitrogen when nonprotein energy was supplied by either glucose or soybean oil; however, in the absence of dietary carbohydrate the requirement increased. In the absence of dietary carbohydrate when nonprotein energy was supplied by soybean oil, diammonium citrate was less effective in promoting growth than L-glutamic acid or L-aspartic acid; DL-serine was still less effective, and DL-alanine and ammonium acetate almost completely failed to promote growth. The addition of carbohydrate to the diet markedly improved growth of chicks fed either diammonium citrate or ammonium acetate, but DL-alanine still failed to promote growth. Although DL-serine was more effective than DL-alanine, it was less effective than either L-glutamic acid, L-aspartic acid or diammonium citrate. Further studies showed that chicks fed a carbohydrate-containing diet in which L-alanine served as the major source of nonessential nitrogen grew at the same rate as chicks fed a similar diet containing L-aspartic acid, although slightly but significantly slower than chicks fed L-glutamic acid. The failure of chicks to grow when DL-alanine served as the major source of nonessential nitrogen in a carbohydrate-containing diet is due to the D-isomer.